Oki’s Largest Keyhole-Shaped Tumulus
Hei Shrine Tumulus is believed to have been constructed in the late 6th century, during the final stages of the Kofun period. Measuring approximately 46 to 48 meters in total length, it is the largest known ancient burial mound in the Oki Islands.
The tumulus was built at the edge of a hillside overlooking the inner part of the Yao Plain. Its prominent location and considerable scale suggest that the individual buried here was likely an influential local leader. The site provides an important clue to the emergence of political authority in the ancient Oki Islands.
A Distinctive Two-Tiered Mound
The mound has the characteristic keyhole shape formed by a circular rear section and a rectangular front section. Both sections were constructed in two tiers.
The rear circular section measures approximately 32 meters in diameter and 5.5 meters in height, while the front section is approximately 20 meters wide and 4.5 meters high. River stones believed to have been used as stone coverings have been identified on the surface of the mound, and fragments of haniwa, the clay figures commonly associated with Kofun-period tombs, have also been discovered.
The presence of haniwa is particularly significant because such finds are relatively uncommon in the Oki Islands. They provide evidence of cultural connections between Oki and the Japanese mainland during the Kofun period.
The Stone Burial Chamber
The burial facility is a horizontal stone chamber located toward the western side of the circular rear section, close to the junction between the front and rear portions of the mound. The chamber originally extended approximately 8 meters.
Much of the ceiling was lost, reportedly as a result of looting and other damage over the centuries. Today, sections of the side walls and rear wall remain, allowing visitors to see traces of the construction techniques used more than a thousand years ago.
An Unusual Chamber Layout
The stone chamber is positioned slightly away from the center of the circular mound. Researchers have therefore suggested the possibility that another burial chamber may once have existed.
The chamber incorporates both natural and split stones, with stones arranged using a corbelled construction technique. These surviving details offer a glimpse into the sophisticated engineering skills employed by Kofun-period builders.
The Connection Between the Tumulus and Hei Shrine
Hei Shrine stands on the southern side of the narrow section connecting the two parts of the tumulus and is the source of the tumulus’s name. The practice of placing a shrine on or beside an ancient burial mound can be found in various parts of Japan.
Such sites demonstrate how ancient burial places could acquire a sacred character over later generations. A tomb originally associated with an ancient political leader gradually became a place of worship and local faith.
Today, the site continues to be carefully maintained by the local community. The coexistence of the ancient tomb and the shrine creates a distinctive atmosphere in which archaeology, history, and living religious traditions come together.
Yao Plain and the Ancient Center of Oki
An Important Political and Cultural Region
The area around the Yao Plain was one of the most important centers of ancient Oki. The location of the provincial government of Oki Province is believed to have been somewhere in this wider area, while the ruins of Oki Kokubunji and Oki Kokubun-niji are located nearby.
These sites indicate that the region played an important role in the administration of Oki under the ancient Ritsuryo system, Japan’s early system of centralized government. The concentration of archaeological and historical sites makes the area particularly valuable for understanding the development of Oki society.
A Landscape of History Spanning Centuries
The importance of this area continued through different periods of Japanese history. During the Kofun period, it was associated with the burial of an influential local leader. Centuries later, during the Nara period, it became the setting for a state-sponsored Buddhist temple. It also played a role in the political history of medieval Japan.
This layering of different historical periods within the same landscape is one of the most fascinating aspects of visiting Hei Shrine Tumulus and its surrounding sites.
Oki Kokubunji and the Continuation of Cultural Heritage
A Provincial Temple Founded in the Nara Period
Nearby Oki Kokubunji Temple was established in 741, following Emperor Shomu’s order to build provincial Kokubunji temples throughout Japan. It became a major center of Buddhist culture and religious practice in Oki.
The temple preserves the legacy of this ancient religious network and provides an important historical counterpart to the much earlier Hei Shrine Tumulus.
A Site Associated with Emperor Go-Daigo
Oki Kokubunji is also traditionally associated with Emperor Go-Daigo, who was exiled to the Oki Islands at the end of the Kamakura period. The temple is said to have served as his temporary residence during his exile, and a stone monument on the grounds commemorates this connection.
This episode adds another important layer to the area’s long history, linking the ancient landscape of Oki with the political upheavals of medieval Japan.
Renge-e Mai: An Ancient Tradition Still Performed Today
Oki Kokubunji is also the setting for Renge-e Mai, a traditional performing art presented every year on April 21. With origins in the Nara and Heian periods, the performance preserves elements of ancient Buddhist dance and music and is designated as an Important Intangible Folk Cultural Property of Japan.
The graceful and solemn dances, sometimes incorporating humorous movements, demonstrate how ancient cultural traditions can remain part of living community life many centuries after their origins.
Visiting Hei Shrine Tumulus
A Quiet Place to Encounter Ancient History
Because extensive archaeological excavation has not been carried out at Hei Shrine Tumulus, the mound retains much of its natural appearance. Surrounded by greenery and quiet countryside, the site offers a peaceful setting for imagining the people and society of the Kofun period.
Rather than being a large museum-style attraction, the tumulus is a place where visitors can experience history through the landscape itself. The shape of the mound, the remaining stonework, and the nearby shrine provide subtle clues to its long history.
Combining the Visit with Oki Kokubunji
Hei Shrine Tumulus is located close to Oki Kokubunji and the ruins of Oki Kokubun-niji. From Saigo Port, the area can be reached by bus in approximately 15 minutes, followed by a walk of around five minutes from a nearby bus stop such as Kokubunji-mae.
Visiting these sites together makes it easier to understand the transformation of Oki’s central landscape, from the burial grounds of powerful Kofun-period leaders to the Buddhist institutions of the Nara period and the historical events of medieval Japan.
A Window into the Ancient History of the Oki Islands
Hei Shrine Tumulus is an important archaeological site for understanding the ancient history of the Oki Islands. Its large scale, distinctive keyhole shape, stone burial chamber, and haniwa fragments point to the presence of powerful local figures and cultural connections with mainland Japan during the Kofun period.
Its location beside Oki Kokubunji and other important archaeological sites makes the surrounding area especially rich in historical interest. A visit allows travelers to follow the story of Oki across centuries, from ancient burial traditions to the introduction of Buddhism and the political history of medieval Japan.
For travelers interested in archaeology, Japanese history, and cultural heritage, Hei Shrine Tumulus offers a quiet but rewarding experience. Standing amid the natural landscape of Dogo Island, it is a place where the distant past remains closely connected with the living traditions of the present.